There exists e.g. according to FR-A-2771161 in the name of the applicant an installation on the one hand consisting of at least the web, the gas-heated radiant elements arranged according to at least one row stretching out in the transversal direction of the web, substantially over its entire width, and, downstream at least one row of radiant elements, at least a transversal convective system equipped with suction and blowing devices to suck at least part of the combustion products produced by the radiant elements and to blow the said part of the combustion products towards the web. In a traditional way, the installation generally also has devices to extract the warm gases resulting from the convective exchanges between the passing web and the said combustion products.
In a traditional way, the suction and blowing devices have a mixing device, such as e.g. a ventilator, that is, for several known reasons, shifted laterally at the outside of the web, in relation to the median longitudinal axis usually at a large, even extremely large, distance in relation to the width of the web.
In that way, the ventilator has to laterally collect the combustion products that are initially divided over the entire width of the web, mix the combustion products and divide them again over the entire width of the web.
Such a mixing entails an important consumption of energy.
In addition, such an installation has suction and blowing ducts that, at least in the transversal direction of the web, have an important size.
These ducts dissipate thermal energy by radiation and convection. There is amongst other things aspiration of cold air that is cooled down in the combustion products.
Because of these different reasons, the temperature of the combustion products blown on the web is considerably lower than the temperature of the combustion products generated by the radiant elements.
Such an installation thus implicates a considerable consumption of mechanical energy and also a considerable loss of thermal energy, thus resulting in considerable investment and operating costs, and also occupies a large surface.